The present invention is directed toward an electrophysiology catheter for studying a patient's heart by stimulating the heart and sensing the resulting activity in order to determine the patient's potential to have an arrhythmia occur under uncontrolled circumstances, and more particularly, toward a defibrillation catheter which may be used to defibrillate the heart if, during the electrophysiology studies, the patient's heart starts to fibrillate.
As is well known in the art, catheters are frequently used with electrodes on the surface thereof for selectively stimulating and/or sensing electrical activity in the body, particularly within the heart. Various electrophysiology studies, such as cardiac mapping and pacing, are conducted using a catheter in order to determine abnormalities in the heart. Generally, a plurality of closely spaced electrodes are placed at the distal end of the catheter where each electrode is coupled to its own connector and is ultimately connected to recording equipment at the proximal end of the catheter. The electrodes sense electrical activity of the heart at localized locations and the resulting activity is recorded.
Electrical energy may also be applied to the electrodes in order to pace the heart. As a result, ventricular tachyarrhythmia may be purposefully induced, or the more lethal ventricular fibrillation may be accidentally induced in the heart. Ventricular fibrillation is an uncoordinated contraction and relaxation of the individual fibers of the heart which produces no blood flow and results in death unless the heart is defibrillated immediately. In order to defibrillate the heart, the electrophysiology catheter must be removed and the patient sedated in order to shock the heart. Typically, a pair of electrodes or paddles are placed across the chest of a patient. Sufficient voltage, i.e., high intensity energy, of, for example 300 to 360 Joules is then applied to depolarize most of the ventricular cells.
This procedure has several disadvantages. For one, the testing must be interrupted in order to defibrillate the heart. The catheter being used for the studies may have to be removed before the electric shock can be applied to the patient. The high intensity of the energy delivered to the patient is traumatic to the patient and may bum the patient's skin. Also, the patient will require a period of recuperation before the testing may continue. As a result, the testing will be delayed and the results may be inaccurate because of the interruption. Furthermore, when tachyarrhythmia or fibrillation occurs, corrective measures must begin immediately. Using the external paddles may delay the defibrillation in that the electrophysiology catheter may have to be removed and the paddles put in position. Not only does this delay increase risk to the patient's life, a high level of energy, for example, 300 to 360 Joules may be necessary in order to defibrillate the heart.
U.S. Pat. No. 5,405,375 recognizes these deficiencies and seeks to overcome them. This patent discloses a mapping catheter which may also be used to defibrillate the heart through the atrium if fibrillation occurs during the mapping. The catheter has a first and second set of a plurality of electrodes located on the distal end. The first set of electrodes is coupled to one connector. The connector is attached to an external defibrillating device. A second electrode may be provided by an additional electrode or a chest wall electrode. The problem with this procedure, however, is that it is rather invasive. That is, a second catheter or electrode must be placed within the patient in order to defibrillate the heart, adding trauma to the patient.